I am running a test data with 1577 nodes and 10036 edges, DiGraph, raw structure all connected, using infomap in igraph. After executing:
on the boundary of raw-structure, there appears several “single node community”, they only have either one in-degree or one out-degree edge. But the algorithm still separated them from the mother community. I also tried leidenalg, but the same issue occurs.
This issue I didn’t find in a research paper or google, and the only possibility I guess is the parameter setting in algorithm. But from theoretical background it is no sense to increase those subgroups to optimize the equation. So I am wondering were there any bug?
Anyone might have the same issue or any suggestion? Thanks and please 
Best Regards
P.S. I am new user and not allowed to upload my dataset.